1. Field of the Invention
Embodiments of the invention generally relate to the field of semiconductor manufacturing processes and, more particularly, to methods of making substrates that have been implanted with arsenic, phosphorus, or boron safer to handle.
2. Description of the Related Art
Integrated circuits may include more than one million micro-electronic field effect transistors (e.g., complementary metal-oxide-semiconductor (CMOS) field effect transistors) that are formed on a substrate (e.g., semiconductor wafer) and cooperate to perform various functions within the circuit. A CMOS transistor comprises a gate structure disposed between source and drain regions that are formed in the substrate. The gate structure generally comprises a gate electrode and a gate dielectric layer. The gate electrode is disposed over the gate dielectric layer to control a flow of charge carriers in a channel region formed between the drain and source regions beneath the gate dielectric layer.
An ion implantation process is typically utilized to implant and dope ions into the substrate, forming the gate and source drain structure with desired profile and concentration on the substrate. During an ion implantation process, different process gases or gas mixtures may be used to provide ion source species such as arsenic, phosphorus, or boron. Arsenic, in particular, will react when exposed to moisture to produce arsenic oxide and arsine gas according to the following reaction:As+H2O→AsH3+AsxOy 
Arsine gas is a highly toxic gas that is also flammable. When high doses of dopant (i.e., about 1×1016 l/cm2 or more) and low implantation energy (i.e., about 2 kV) is applied, the dopant does not implant deeply into the layer stack. Thus, more dopant is present near or at the surface of the layer stack and may be exposed to moisture upon removal from the chamber. The arsenic residing near the surface may react to undesirably form arsine gas.
Therefore, there is a need for a method to prevent toxic compounds from forming after dopants have been implanted.